Electrodeposition and characterization of Ni--Fe alloys obtained under magnetohydrodynamic (MHD) control as thin layers

K. Msellak - J.-P. Chopart - O. Jbara - O. Aaboubi - J. Amblard

DTI, CNRS UMR 6107, UFR Sciences, BP 1039, 51687 Reims Cedex 2, France }

Abstract
The electrodeposition of nickel--iron alloys on a copper substrate in the presence of a magnetic field was studied both by electrochemical and physical techniques. The results clearly show that the Ni--Fe film composition and morphology change due to an increase of the surface concentration of the inhibiting species Fe(II) by the MHD effect. The iron concentration in the alloy increases with the magnetic field amplitude, and can be twice as greater from 0 to 0.9 T. In addition, X-ray mapping demonstrates a high homogeneity of the distribution of nickel and iron atoms throughout the surface, under the magnetic convection, except in the vicinity of the hydrogen bubbles, where a disturbance of the distribution of nickel and iron atoms can be observed. These aspects were also confirmed by a kinetic analysis of the electrodeposition, where an inhibition of the electrode surface enhanced by the MHD convection was found. This reduces the electrolysis current, as the magnetic field increases. EIS measurements highlight the same inhibition phenomenon that can be evidenced by the increase of the characteristic inductive loop in Nyquist diagrams. Tables 2, Figs 5, Refs 8.